Artificial tooth-crown



-('Model.) W. G. A. BONWI-LL' Artificial Tooth Grown;

"No. 238,334. P ate nted March 1,1881.

Nffl ifis PHOTO LITHOGRAPHEE WASHINGTON u c UNITED STATES ATENT FFICE.

WILLIAM G. A. BON WILL, OF PHILADELPHIA, PENNSYLVANIA.

ARTIFICIAL TOOTH-CROWN.

SPECIFICATION forming part of Letters Patent No. 238,334, dated March 1,1881.

I Application filed December 24, 1880. (ModeL) To all whom it mayconcern:

Be it known that I, WILIIAM G. A. BON- WILL, of Philadelphia, in theState of Pennsylvania, have invented certain new and useful Improvementsin Artificial Tooth-Crowns and the method of mounting or attaching thesame in place, of which the following is a specification.

The object I have in view is principally to attach an artificialtooth-crown to the natural root or roots in such a manner that the crownshall be held in' place in a most secure and permanent manner. The crownwhich I have devised is, however, also equally applicable to plate-work,so called.

My invention has relation to that in ethod of securing the crown inwhich the crown is fitted upon and secured to a pin held in place in andprojecting from the root, said pin being held to both crown and root byamalgam. Hitherto, so far as I am aware, the point at which the amalgamhas united the crown to the pin has been near the base of the crown, andthe consequence has been that the tooth-crown is incapableof-withstanding the strain that frequently comesupon it,and consequentlybreaks away or separates from the root.

The gist of my invention consists in extending the cavity through thecrown to or very near the grindingor cutting surface thereof, and ingiving the said cavity at this point retaining form, so that the amalgamwhich fills this portion of the hollow or opening in this crown aroundthe pin may act to take hold and retain in place the crown. By thusextending the support to, or nearly to, the grinding-surface of the'tooth, and holding the crown at this point, I secure the latter in amost permanent manner to the root and impart to it the needed strengthto resist the lateral thrusts or strains to which it must necessarily besubjected from time to time.

The nature of myinvention and the manner in which the same is or may becarried into effect will be understood by reference to the accompanyingdrawings, in which- Figurelis a vertical central section of an incisortooth-crown made in accordance with my invention. Fig. 2 is a like viewofthe same mounted and secured in place on a root,

all the parts being represented in section. Fig. 3 is a plan of atooth-crown such as in Fig. l, with a modified form of opening therein.Fig. 4 is a vertical section of the same on x a, Fig. 3. Figs. 5, 6, and8 represent, in section and perspective, other forms of tooth-crowns.Fig. 7 is a sectional view of the tooth-crown in Fig. 8, mounted andsecured in place on a root.

All of the tooth-crowns shown in the drawin gs are hollow or virtuallyopen from end to end. The opening a in the tooth-crown shown in Fig. 1does not extend out through the cutting edge or surface of saidcrownwhich is that of an incisor-but it extends to a point very nearthat edge, and out through the rear or lingual or palatal face of thetooth, as shown. The opening a is enlarged at the base of the tooth, asseen at a, the said hollow being formed with sides which slope graduallytoward the contracted part to, having such form as shall, when thetooth-crown is pressed in place upon the root, tend to force the amalgamplaced in said enlarged portion a toward the pin 12, and into and moreor less through the longitudinal passage a around thepin, as shown inFig. 2.

At or near the grinding or cutting face of the crown the walls of thecavity a have retaining form. This retaining form may be obtained byproperlyshapin g the mouth a of the cavity, or by undercutting thelateral walls of the said passage orcavity at its outer end, as shown inFig. am 0. In some instances I prefer to give the passage to atriangular form in cross-section, as shown in Fig. 3, which form ofamalgam or gum without unduly weakenin g the shell of the crown. Iremark that when the cavity is undercut, as shown at c in Fig.

3, the mouth a of the cavity may be closed before the tooth is burned.to leave it open, inasmuch asit will forma vent to permit escape ofsurplus cement or amalgam. 4

The'crown shown in Fig. 5 is a bicuspid, and in Fig. 6 a molar. Thesecrowns are longitudinally hollow, and have at the coronal opening aretaining form, as indicated at d. In case more than one pin is employedthe crown may have a like number of passages, a,

I prefer,.however,-

ICC

s admits a comparatively large body or filling leadingfrom the enlargedbasal cavity'a, as indicated in Fig. 6; or the several pins may passthrough one opening, as indicated in Fig. 7.

Root B of the tooth is excavated in such a manner that its cavity shallcorrespond at its outer edge with the like edge of the basal portion ofthe cavity in the crown. By this means the bone portion of the tooth isentirely protected by the cement from the action of the 10 juices of themonth, since the cement extends before described.

to the outer surface of the root at the point of its junction with thecrown.

The method which I preferably employ of attaching the artificial crownto the natural root is as follows: I first fill the previouslypreparedroot with amalgam or cement, and then insert into the amalgam whilestill plastic a pointed tool, of a diameter slightly less than that ofthe metallic pin to be afterward inserted. After the tool has beenwithdrawn the barbed metallic pin is forced into the hole thus formedfor it, and the cement, by means of .a suitable instrument, is closelypacked around the pin, which should be keptin about the center of theroot-cavity. The crown is then placed over the pin in order to determinewhen the latter is in proper position and of a proper length to extendto, or nearly to, the grinding or cutting face of the crown. The crownis then withdrawn and additional amalgam is placed about the pin in theroot. The crown is next filled to excess with the amalgam, (mixed to setmore quickly than that used in the root,) and is then forced over thepin and firmly but gradually pressed to its proper position on the root.By this means not only is the pin securely fixed in place in both crownand root, but the amalgam or cement in the two is also firmly pressedinto one coherent and homogeneous mass about the pin, the sloping wallsof the enlarged cavities in the 'upper part of the root and the basalportion of the crown tending to drive the plastic material toward thepin, and thus effect a more perfect union of the parts, the pinconsisting of the central stem and the amalgam exterior virtually havingthe exact shape of the cavity as the crown or root, as indicated inFigs. 2 and 7, with retaining form at or near the grind ing-surface ofthe tooth. At the coronal openingthe amalgam around the pin is, by meansof a suitable instrument, finished off, and the work is then complete.

Where the artificial tooth-crown is to be attached to an artificialbase-plate of rubber,

- celluloid, or metal, instead of the natural root of the tooth, ametallic pin of great strength and stiffness is embedded into thebase-plate, and the crown fixed upon it at the same time or by asubsequent operation, substantially as My invention here offers theadvantage (as it does in the case of the natural. root) that a crown,when broken from the pin, may be replaced with another by simplyremoving a portion of the hardened cement from about the pin andproceeding as in the first instance in pivoting. In the case of rubberplates, the opening in the crown may be first filled with the softenedunvulcanized rubber, the pin then inserted, and the body of the platemolded so as to firmlyembrace the other end of the pin, so that thesubstance of the plate will extend in a homogeneous mass into theextremity of the tooth or crown, receiving additional strength andrigidity from the metallic pin inclosed in it; or, as above described,the crown may be placed onto the plate after thevulcanization of thesame by removing the tooth-crowns after they have been suitablyarranged, and returning the same to their places by any of the cementsin use.

With reference to the triangular form of a cavity shown in Fig. 3, withthe base of the same toward the face or labial surface of the tooth, andthe apex toward the palatal or lingual surface of the same, I remarkthat the advantage of this form of opening is, that the whole strain isthereby transferred to the front of the tooth-crown, thus enabling me tomake the crowns of extreme thinness on the palatal or lingual surfacesand at the base without impairing their effective strength.

Tooth-crowns embodying my invention may be made either singly or inblocks of two or more, with or without artificial gum attached.

I am aware that prior to my invention artificial tooth-crowns had beenmade with a vertical opening extending through the tooth and countersunkon the palatal surface for the head of a screw, which was relied upon tofasten the crown to the root.

I am also aware that there has been a crown composed of either metalalone or porcelain, or a crown of both porcelain and gold, having alarge opening at the base, which was to be filled with cement and placedover the pins previously fixed in the natural root.

I am also aware that an artificial toothcrown provided with alongitudinal cavity has been mounted on a natural root by means of a pinand amalgam filled around the pin into the cavities in the root andcrown. I am not aware, however, that a crown has before been providedwith a cavity enlarged at the base, extending through to or near thegrinding or cutting surface, and made at the latter point of retainingform, so as to anchor and hold the crown at said point by means of theamalgam filling around the pin.

WhatI claim, and desire to secure by Letters Patent, is

1. An artificial tooth-crown, having an opening or cavity of a size tocontain the pin and surrounding amalgam, which extends from the base ofsuch crown to or near the grinding or cutting surface of the same, atwhich point such opening is enlarged or undercut, so as to haveretaining form, substantially as set forth.

'2. A longitudinally-hollow artificial toothcrown having an enlargedbasal cavity and coronal opening of retaining form, substantially as andfor thepurposes hereinbefore set forth.

3. The method described of mounting artificial tooth-crowns on roots,which consists in making the crown hollow, with enlarged basal cavity,and a coronal opening of retaining form, and then uniting said crownwith the root on which it is placed by means of a pin and amalgam orcement, which fills the cavi- IO ties in the root and crown around thepin, and

extends up into and is anchored in or near the coronal opening of thecrown, substantially as hereinbefore set forth.

In testimony whereof I have hereunto set my hand.

WM. G. A. BONWILL. Witnesses:

S. M. GAYLEY, AND. W. GAYLEY.

